The present invention relates to a method for three-dimensionally, optically measuring measuring objects by comparison with a reference object, where image data of the measuring object are acquired and compared to image data of the reference object, and the measuring object is directly or indirectly assessed with regard to deviations from the reference object.
In a conventional method, a measuring object undergoes a good-bad assessment by comparison to a reference object, e.g., at the end of a manufacturing operation, the assessment being performed visually, for example. In this context, three-dimensional image data of the reference object can be acquired, for example, and compared to the image data of the measuring object. The reference object and the measuring object must be considered in the same position for a reliable assessment. A relatively complicated adjustment is performed to align the positions.
It is an object of the present invention to provide a method that enables the measuring object to be reliably measured and assessed with relatively little expenditure.
The above and other beneficial objects of the present invention are achieved by providing a method as described herein.
According to one example embodiment of the present invention, it is provided that the measuring object and/or the reference object or a holographic recording of the measuring object and/or the reference object is/are rotated relative to one another about at least one axis, the image data of the measuring object being acquired and the comparison being performed in various, relative rotational position, that in the various comparisons, an evaluation regarding a maximum agreement of the measuring object with the reference object is performed, and that the assessment of the deviation is performed in the rotational position determined by the maximum agreement.
Rotating the reference object and measuring object or their holographic recordings relatively to one another and comparing the image data during the rotation and the evaluation regarding the best agreement automatically determines those relative rotational positions in which the reference object and the measuring object or their holographic recordings (holograms) have the same orientation. In this specific rotational position, the measurement of the measuring object and the assessment as to whether deviations exist with respect to the reference object are able to be reliably performed, respectively, since errors due to a positional deviation of the two objects are ruled out. In this context, the same evaluation unit may evaluate the comparisons and the assessment.
The measure of holographically recording the measuring object during a production process into which it is incorporated contributes to the method being performed quickly.
An integration of the method during production may be achieved in that the measurement is performed with the assessment of the deviation of the measuring object from the reference object during a production process, an automatic assessment being possible, yet a visual assessment also being possible.
A further possibility for simply implementing the method provides for the image data that three-dimensionally represent the reference object to be stored from the start in an evaluation unit in which the comparison of the acquired image data of the measuring object regarding the maximum agreement and the assessment of the deviation are also performed.
The measure that the image data of the measuring object and/or of the reference object are acquired by a camera contributes to a quick and reliable implementation of the method.
One example embodiment for a simple automatic or visual assessment of the method provides for the deviations of the measuring object from the reference object to be directly assessed following the interferometric superimposition of the two by comparing the obtained interference pattern to a reference interference pattern. The interference pattern may be assessed in a particularly simple manner with respect to characteristic differences in the case of a deviation of the measuring object from the reference object.
One example embodiment for a simple implementation of the method provides for the reference object or its holographic recording to be situated in a reference arm of an interferometer and the measuring object or its holographic recording in an object arm of the interferometer, and for a reference light wave coming from the reference object or its holographic recording and an object light wave coming from the measuring object or its holographic recording to be superimposed at a beam splitter, and for the interference pattern obtained in this manner to be recorded by the camera.
A further example interferometric method provides for the measuring object and a light-deflecting element, in particular a mirror, to be illuminated and light waves reflected by the measuring object and the mirror to be directed at a hologram of the reference object while it is rotated, and for the light superimposed on the hologram to be determined by the camera.
It is provided for the reliable implementation of the method that the holographic recordings of the reference object and/or of the measuring object are obtained via a suitable device that generates the beam path of the interferometer.
Additional example embodiments of the method relate to the assessment being visually performed at a display device on the basis of a representation of prepared image data generated by an evaluation unit or automatically performed in the evaluation unit on the basis of predefined or predefinable criteria.